From d10ad8444f29658d56eb7650a3781bc6cebe2620 Mon Sep 17 00:00:00 2001
From: Dov Murik <dovmurik@linux.ibm.com>
Date: Thu, 1 Jul 2021 12:20:40 +0000
Subject: [PATCH] OvmfPkg/QemuKernelLoaderFsDxe: call VerifyBlob after fetch
 from fw_cfg

In QemuKernelLoaderFsDxeEntrypoint we use FetchBlob to read the content
of the kernel/initrd/cmdline from the QEMU fw_cfg interface.  Insert a
call to VerifyBlob after fetching to allow BlobVerifierLib
implementations to add a verification step for these blobs.

This will allow confidential computing OVMF builds to add verification
mechanisms for these blobs that originate from an untrusted source
(QEMU).

The null implementation of BlobVerifierLib does nothing in VerifyBlob,
and therefore no functional change is expected.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
Co-developed-by: James Bottomley <jejb@linux.ibm.com>
Signed-off-by: James Bottomley <jejb@linux.ibm.com>
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
---
 OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c b/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c
index c7ddd86f5c..6832d563bc 100644
--- a/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c
+++ b/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c
@@ -17,6 +17,7 @@
 #include <Guid/QemuKernelLoaderFsMedia.h>
 #include <Library/BaseLib.h>
 #include <Library/BaseMemoryLib.h>
+#include <Library/BlobVerifierLib.h>
 #include <Library/DebugLib.h>
 #include <Library/DevicePathLib.h>
 #include <Library/MemoryAllocationLib.h>
@@ -1039,6 +1040,14 @@ QemuKernelLoaderFsDxeEntrypoint (
     if (EFI_ERROR (Status)) {
       goto FreeBlobs;
     }
+    Status = VerifyBlob (
+               CurrentBlob->Name,
+               CurrentBlob->Data,
+               CurrentBlob->Size
+               );
+    if (EFI_ERROR (Status)) {
+      goto FreeBlobs;
+    }
     mTotalBlobBytes += CurrentBlob->Size;
   }
   KernelBlob      = &mKernelBlob[KernelBlobTypeKernel];